The invention relates to an impeller for a fluid energy machine including a rotor with a hub provided with rotor blades having curved transition regions between the hub and the blades.
Presently, fluid energy machines are provided in the form of exhaust gas turbo-chargers including compressors and turbines which are used in connection with combustion engines for power enhancement. It is therefore desirable that these fluid energy machines have a service life which corresponds at least to that of the combustion engines. Contrary to combustion engines, these fluid energy machines however have extremely high operating speeds of up to, and even far over, 100,000 rpm. Due to the high centrifugal forces the tensile strength of the impellers of the fluid energy machine must meet stringent requirements.
DE 10 2010 020 307 A1 discloses an impeller wheel of a fluid energy machine in the form of a radial compressor. This impeller comprises rotor blades which are fixedly connected to a hub of the impeller via transition regions. Contrary to conventional compressor wheels whose transition regions have an identically formed curvature both in the longitudinal direction of the rotor blade and in the circumferential direction of the hub, the compressor wheel of this unexamined German application exhibits a changing curvature in the longitudinal direction of the rotor blade.
However, the manufacture of such an impeller with different radii of the transition region over the length of the rotor blades is relatively expensive.
It is the principal object of the present invention to provide an impeller for a fluid energy machine which exhibits a very long service life and simultaneously is relatively inexpensive to manufacture.